A small study suggests that stem cells from a stranger may be as good as a patient's own in undoing the damage after a heart attack has weakened the heart's ability to pump blood. The study hints at the possibility that stem cells could be banked, much like blood is banked, to deal with a medical emergency — in this case, heart attack.

The findings on the study of a kind of stem cell called mesenchymal cells were presented at the annual meeting of the American Heart Association this week and published online in the Journal of the American Medical Association.

"We believe the basic message of the study is that this procedure is safe and that future, larger studies are warranted," lead author Dr. Joshua Hare, director of the Interdisciplinary Stem Cell Institute at the University of Miami, told reporters at a national briefing.

The researchers studied patients following heart-attacked-caused ischemic cardiomyopathy, the most common cause of heart failure. According to the Texas Heart Institute, it occurs when the heart suffers a temporary blood shortage, resulting in loss or weakening of heart muscle tissue and reduction in its ability to pump blood.

Whether a donor's cells will work as well is important, because it can take up to two months to grow millions of cells needed for transplant and there's no time in the immediate wake of a heart attack, Stephanie Dimmeler, molecular cardiology section chief at University of Frankfurt in Germany, told U.S. News and World Reports' HealthDay. Dimmeler was not involved in the study.

For the study, researchers looked at 30 patients from Miami who had enlarged hearts that had been damaged by an earlier heart attack. Half received their own mesenchymal stem cells, while the other half received the same kind of cell, but from young, healthy donors. The heart patients each received 20 million, 100 million or 200 million stem cells into 10 scarred left ventricular sites. The researchers then followed their cases for 13 months.

Mesenchymal stem cells are taken from bone marrow and lack a feature on their surface that triggers an immune response called rejection, Hare told the Associated Press. They are multipotent cells that can change to become a number of different types of cells, including bone, muscle, ligament, cartilage, fat and tendon, according to mesenchymalcells.org, which is dedicated to providing information about that particular type of cell. The heart is a muscle tasked with pumping blood throughout the body.

The heart attacks of the study participants were in the past, some as long as 30 years ago, but all the subjects had hearts so weakened by scarring that they were unable to pump blood well.

They obtained the marrow from which stem cells were harvested by advertising for donors and removing it from the hip bone with a needle. They didn't have to match blood or tissue at all. The stem cells were taken from the marrow and then grown for a month at Johns Hopkins University in Baltimore, then returned to Miami for use in patients. No surgery was involved, the researchers said. Instead, the cells were pushed into the heart near scarring using a catheter inserted near the groin.

Hare said they saw scarring in the heart reduced by 33 percent in both groups and that misshapen hearts regained their earlier shape, also a sign of reduced scarring. Function also improved at comparable rates based on a walking test for both those with their own and donor stem cells. The researchers documented an immune reaction in only one patient, and it was described as "very low level."

The findings, however, are not a green light for a cure, but rather an indication that further study is warranted, the researchers said.

Still, one of the study's subjects, Juan Lopez, told Associated Press that after he received his own cells, his symptoms improved to the point that, at age 70, he could return to his work as an engineer and sales manager for a roofing manufacturer and ride an exercise bike.

"It has been a life-changing experience," the wire service quoted him. "I can feel day by day, week by week, month by month, my improvement. I don't have any shortness of breath and my energy level is way up there. I don't have any fluid in my lungs."